The Myxobacteria are a group of gram-negative bacteria that undergo a true multicellular development and a primitive differentiation. They provide a simple system for investigating the regulation of development because they resemble more familiar bacteria in structure and in their accessibility to genetic manipulation through transduction and gene cloning. Myxobacteria grow vegetatively like other bacteria, but when nutrients become limiting, Myxobacteria aggregate to form multicellular fruiting bodies. Within nascent fruiting bodies cells sporulate, changing - in the case of Myxococcus xanthus - from long rods to spherical spores, which are dormant. Under appropriate conditions, the spores germinate to give rod-shaped growing cells. The objective is to find out, in molecular and cellular terms, how this simple development process is regulated and how the cells interact with each other to coordinate development. The signal molecules that cells use when they interact with each other in the formation of fruiting bodies will be isolated and identified. For this purpose, a set of mutants that behave as if defective in producing individual signals will be used as bioassay cells. The genetic program that regulates development will be studied using mutants and a transposable probe for promoter activity. The tools for these investigations are biochemistry and molecular genetics. In the long term, this work may facilitate the understanding of human developmental birth defects and speed their medical treatment.